Tandem-type image forming apparatuses using electrophotography are known. Image forming apparatuses of this type include photosensitive members corresponding to the toner colors of yellow, magenta, cyan, and black. Image formation process parts, such as developing cartridges and charging devices, typically are provided around the respective photosensitive members for the various colors. Image formation is implemented by transferring a toner image formed on each photosensitive member by toner of each color onto a sheet. In such image forming apparatuses, an openable cover often will be provided at a top of a main casing of the image forming apparatus. By opening the cover, various parts, such as the developing cartridges, disposed inside the image forming apparatus can be replaced with new ones, or a paper jam occurring within the main casing can be cleared. In other image forming apparatus structures, a drawer may be provided in which the developing cartridges are loaded. By pulling the drawer to a predetermined position from the main casing, replacement of the developing cartridges can be performed.